ASAS/ADSA Food Safety: Bacteria Detection

Crohn’s disease in humans has strong similarities to Johne’s disease in cattle, but with a poorly defined etiology. Mycobacterium paratuberculosis, the causative agent of Johne’s disease, has been linked as a causal agent of Crohn’s disease in humans. However, evidence to date does not prove that Crohn’s disease is caused by M. paratuberculosis and may, in fact, be a multifactorial disorder. Regardless, it has become a concern for the dairy industry as consumer confidence has been influenced by reports that pasteurization may not destroy the bacterium. Efforts to eliminate M. paratuberculosis from the food chain would require rigorous control and management programs for this disease on the farm. Although voluntary programs are in place in many states in the US, it will still be many years before the spread of this disease is attenuated. In the meantime, we must rely on methods that guarantee that potential contaminating agents such as M. paratuberculosis are destroyed in food products post-harvest. Studies to determine optimal methods of pasteurization by heat treatment are underway in many countries, including the US. An alternative method of destruction is the use of ionizing radiation. In the present study, we examined the effects of radiation on milk experimentally inoculated with 104 and 108 cfu M. paratuberculosis/ml of milk. Milk was exposed to either 0, 5 or 10 kGy of radiation (1.2 kGy/hr) and cultured for viable M. paratuberculosis. Results from this study demonstrate that M. paratuberculosis was effectively destroyed by gamma radiation at either dose. Thus, ionizing radiation may prove to be an alternative method for destruction of potential contaminants in dairy foods.